title: Chronic glucolipotoxic conditions in pancreatic islets impair insulin secretion due to dysregulated calcium dynamics, glucose responsiveness and mitochondrial activity.
abstract: BACKGROUND
  In the progression towards diabetes, glucolipotoxicity is one of the main causes of pancreatic beta cell pathology. The aim of this study was to examine the in vitro effects of chronic glucolipotoxic conditions on cellular responses in pancreatic islets, including glucose and fat metabolism, Calcium mobilization, insulin secretion and insulin content.
  
  
  RESULTS
  Exposure of islets to chronic glucolipotoxic conditions decreased glucose stimulated insulin secretion in vitro. Reduced protein levels of Glut2/slc2a2, and decreased glucokinase and pyruvate carboxylase mRNA levels indicated a significant lowering in glucose sensing. Concomitantly, both fatty acid uptake and triglyceride accumulation increased significantly while fatty acid oxidation decreased. This general suppression in glucose metabolism correlated well with a decrease in mitochondrial number and activity, reduction in cellular ATP content and dampening of the TCA cycle. Further, we also observed a decrease in IP3 levels and lower Calcium mobilization in response to glucose. Importantly, chronic glucolipotoxic conditions in vitro decreased insulin gene expression, insulin content, insulin granule docking (to the plasma membrane) and insulin secretion.
  
  
  CONCLUSIONS
  Our results present an integrated view of the effects of chronic glucolipotoxic conditions on known and novel signaling events, in vitro, that results in reduced glucose responsiveness and insulin secretion.
authors.affiliation: Connexios Life Sciences Pvt Ltd., No. 49, First Main road, 3rd phase, JP Nagar, Bangalore 560 078, India.
authors.forename: Baggavalli P
authors.initials: BP
authors.lastname: Somesh
authors.forename: Mahesh Kumar
authors.initials: MK
authors.lastname: Verma
authors.forename: Manoj Kumar
authors.initials: MK
authors.lastname: Sadasivuni
authors.forename: Anup
authors.initials: A
authors.lastname: Mammen-Oommen
authors.forename: Sanghamitra
authors.initials: S
authors.lastname: Biswas
authors.forename: Pavagada C
authors.initials: PC
authors.lastname: Shilpa
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Reddy
authors.forename: Aggunda N
authors.initials: AN
authors.lastname: Yateesh
authors.forename: Puttrevana M
authors.initials: PM
authors.lastname: Pallavi
authors.forename: Siddaraju
authors.initials: S
authors.lastname: Nethra
authors.forename: Rachapalli
authors.initials: R
authors.lastname: Smitha
authors.forename: Korrapati
authors.initials: K
authors.lastname: Neelima
authors.forename: Usha
authors.initials: U
authors.lastname: Narayanan
authors.forename: Madanahalli R
authors.initials: MR
authors.lastname: Jagannath
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005227:Fatty Acids / Q000378:metabolism; D005941:Glucokinase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D051273:Glucose Transporter Type 2 / Q000378:metabolism; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D023421:Models, Animal; D010168:Palmitates / Q000378:metabolism / Q000494:pharmacology*; D011766:Pyruvate Carboxylase / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014280:Triglycerides / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D051273:Glucose Transporter Type 2; D007328:Insulin; D010168:Palmitates; D014280:Triglycerides; D000255:Adenosine Triphosphate; D005941:Glucokinase; D011766:Pyruvate Carboxylase; D005947:Glucose; D002118:Calcium